Food is often placed in a transparent plastic container that includes a base with a large volume cavity that holds the food and with a cover or lid that closes the cavity. Buyers want to be assured that, after the food was placed in the container as by a clerk at the food store, that the container has not been opened. There is a possibility that another customer has secretly opened the container enough to taste a bit of the food before closing it (and possibly leaving germs from his/her finger in the food). Potential buyers want to be assured that this has not happened. A container constructed by the container manufacturer that allowed a clerk at the store to automatically activate a device that clearly indicated to a potential customer whether or not the container has been opened since it was first closed by the clerk, would be of value.